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The Tall Boys

07-19-2012, 10:40 AM

These speakers debuted at InDIYana 2012 with only couple hours of listening/tweaking on the crossover. They sounded pretty good to my ears, but I thought I could get the balance a little better and maybe even cut down on the number of components in the crossover. Well, after lots of tweaking I am finally satisfied with the balance, although at the cost of a few extra components. It is a full BSC design as the woofers are well away from the floor boundary and all the drivers are small - you could never tell by listening, though. I thought they showed up pretty well at MWAF, but no love from the judges amongst this years stiff competition.

The Tall Boys are a 6" x 7" x 50" 3-way TMWW with the Fountek FR88EX at the heart, covering about 4 octaves from 290Hz to about 2300Hz. This is a fantastic driver and this will not be the last time I use the little guy for midrange duty. The top end is covered by an Audax TW025A0 and the bottom by a series pair of ND105-4s. The tweeter does its job well, but it took a lot of coaxing to deal with the combination of its severely rising upper end and the diffraction bump (due to the narrow 6" cabinet) at its bottom end. The ND105-4s, on the other hand, were a treat to work with. They do bass good! I'm not sold on their midrange qualities, but a pair of them loaded into a 0.64ft3 cabinet tuned to 40Hz really provides a solid bottom end to the system. I've given them a few rigorous workouts with my 150w/channel NAD 2600 and some bass heavy tracks and they HANDLE their BUSINESS. With an F3 of about 40Hz, no sub is necessary with music.

These speakers are a blast to listen to and they take up almost no floor space, even with the necessary 9" x 10" base (they WILL tip over without the bases). There's something very enjoyable about listening to a full range speaker that is only 6" wide. The tweeter is higher than is normally recommended, which puts the average seated listener slightly below the design axis, but that also puts the average standing listener only slightly above the design axis and also raises the presentation in general, which is a step in the right direction for vocal realism IMO.

The enclosure as pictured consists of a 2-piece 3/4" solid oak baffle and 1/2" MDF everywhere else. The top and bottom sections of the baffle are separately removable for convenient changes. The baffles are held on by deck screws with small, attractive heads screwed right into oak corner blocks glued to the walls/window braces. The oak is hard enough and the screw threads coarse enough to facilitate multiple removals and replacements of the baffles - this was WAY easier than using threaded inserts and I will probably do this every time I have a removable baffle from now on. The finish is straight polyurethane on everything, which substantially darkened the MDF to a milk chocolate color - super easy and doesn't look too bad.

The top 9" of the cabinet is separated from the bottom to give the Fountek about 0.15ft3 to breathe in - I filled the whole space with fiberglass. Below that solid shelf, there are window braces about every 11" down the length of the cabinet. The woofer enclosure was modeled for me by DIY Speaker Guy to minimize 1/4 wave resonance issues, which resulted in a port on the opposite end of the 38" long internal cavity from the woofers. The stuffing amount/placement was chosen by ear, which I can only describe as a medium amount in the top half of the line. There was a huge audible difference between no stuffing and too much stuffing, BTW.

-The mid and tweeter are flush mounted, but the woofers are rear mounted for aesthetic purposes. The increase in z-axis spacing is negligible at the 300Hz-ish crossover point.

-System impedence is easy-breezy, above 5 ohms for most of the spectrum, dipping to 4 ohms at 4kHz and a phase that stays above -30 degrees across the whole spectrum.

Comment

It's got a pretty sweet sound to it, and I actually like the look, but it wasn't the easiest tweeter to work with in such a narrow box. The rising top end and the relatively high diffraction bump required some love in the crossover. Considering the smooth sound, the metal faceplate, and the $28 price point, I think it is a pretty good value. I'm a little surprised it's not used more often as a value tweeter.

6thplanet - thanks for the compliment! And congrats to you for placing with your Open Invit8tions. That is an awesome design and very well executed.

Comment

Could these be re-worked using the Aurasound NS3-193-8A1 3" for the woofers? I've got 4 of them and it would save me some cash if I try to build these. I've also got a pair of the Founteks so I'd be a good way there in terms of parts.

Maybe they could be rigged into the box dimensions used for Jim Griffin's Aura T-line mtm.

Comment

I think that replacing the ND105s with NS3s could work out pretty good - there's nothing special about that lowpass on the woofers, but it would a least have to be modified to accommodate the 4ohm load of the 2 NS3s in parallel instead of the 2 ND105s in series. A little efficiency matching might be necessary, too, but the mid is padded by a single resistor before the crossover, so changing that has very little effect on the transfer function other than a direct offset. Let me know if you want to pursue it and I'll help you model the crossover (I won't be much help in the T-line department, though).